He was elected a fellow of the Royal Society in 1840, and in 1892 was awarded one of the royal medals for his work on photometry and stellar parallax.

He found the light of the sun to be 300 times more intense than that of the moon, and thus made some of the earliest measurements in photometry.

It has thus come about that astrophysics owes its recent development, and its recognition as a distinct branch of astronomical science, to the combination of the processes involved in the three arts of spectroscopy, photography and photometry.

He wrote numerous papers on photometry and spectrum analysis in Poggendorff's Annalen and Berichte der k.

The temperature of the sun and of the electric spark, others again with electro-photometry and the chemistry of the electric arc. With Professor J.

The embarrassing subject of photographic photometry has also been attacked by Prof essorPickering.

By adapting to this instrument various ingenious devices he was enabled to employ it in a great variety of investigations, connected especially with photometry, hygroscopy and the temperature of space.